Apparatus for stabilizing the movement of opposed pistons in internal combustion engines



July 9, 1935. R. P. PESCARA' 2,007,305

APPARATUS FOR STABILIZING THE MOVEMENT OF OPPOSED PISTONS 1N INTERNAL G OMBUSTION ENGINES Filed Jan. 5, 1935 3 Sheets-Sheet l 7 Wig Z Raul partera;- Pescara July 9, 19315. R. P, PESCARA APPARATUS FOR STABILIZING THE MOVEMENT 0F OPPOSED PISTONS IN INTERNAL COMBUSTION ElK'rINlSSl Filed Jan. '5, 1935 3 Sheets-Sheet 2 BVENTDR lm5 sm July 9,1935-v R. P. PESCARA 2,007,305

l APPARATUS FOR STABILIZING THE MOVEMENT OF OPPOSED PISTONS IN INTERNAL COMBUSTION ENGINES Filed Jan. 5, 1935 5 Sheets-Sheet 3 INVENTOR Ram Egtefafs Pescara Patented July 9, 1935 UNITED STATES PATENr oFrlc APPARATUS FOR STABILIZING THE MOVE- MENT F OPPOSED PISTONS IN INTERNAL COMBUSTION ENGINES Raul Patcras Pescara, Paris, France -Application January 5, 1933, Serial No. 650,351 In France March 17, 1932 "16 claims. (ci. 23o- 56) driven directly by internal combustion.

In motor compressors providedwith opposed pistons of the type above referred to thepistons are subjected on their return stroke-tothe action of the compressed air cushion contained in a tors prior Patent No. 1,732,693, issued October 22, 1929, that variations in the energy for the return, stroke caused by variations in the length of the pistons motive stroke (which will hereafter be called compression stroke) may be compensated by providing additional closed clearance spaces containing air or an inert gas, the latter providing energy increasing in proportion to the length of the pistons compression stroke.

In actual practice, it is found that the compensation thus obtained is notjalways rigorous, since the energy furnished by the expansion of compressed air in the compression chamber in the course of the return stroke varies directly in proportion to the length of the pistons compression stroke, while the energy furnished by the compressed iiuid functioningv as compensator varies also with the length of the pistons compression stroke but in accordance with a more complicated thermo-dynamic law.

One of the objects of the present invention is to provide a method and apparatus for rigorously compensating variations in the length of the pistons compression stroke so that the piston always returns to thefsame point prior to each explosion.

Another object lis to provide a single stage motor-compressor wherein compensation is obtained in the manner above indicated.

A further object is to provide a multiple Vstage motorcompressor acting to properly compensate variations in the length of the motive stroke.

Still further objects will appear in the course of the detailed description n'ow to be given with the accompanying -drawings, wherein:

reference to Fig. 1 is a diagrammatic section through a singlegfstage motorcompressor illustrating one possible embodiment of th' invention;

Fig. 2 illustrates, in the same manner as Fig. 1, a second single stage motorcompressor assembly; Fig. 3 shows a pair of diagrams `representing the energy relations during the compression and return strokes of the piston and the same relations 5 for the compensating auxiliaries:

Fig. 4 is a diagram showing the energy relations during compression, return and compression and.V for all of these combined;

Fig. 5 is a diagrammatic section through a two- 10 stage motorcompressor embodying a second possible form of the invention;

Fig. 6 includes a pair of diagrams showing the energy relations during compression at each of the two stages; v

Fig. '7 is a. diagram showing the curves of variation in energy during the returnstroke;

Fig. 8 illustrates in a manner similar to Fig. 5 a second form of two-stage motorcompressor;

and

Fig. 9 representsyin ydiagrammatic section, a third two-stage motor-compressor.

Referring to Figure 1 of the drawings, there is shown one half of a motor compressor assembly of the opposed, aligned piston type described in the inventors patent above referred to and composed of the following elements.: a pair of staged pistons l, 2, 3 mounted to move in aligned cylin. ders 9, 5 and 6 respectively, cylinder 9 forming part of. thev motorvassembly, cylinder 5 part of the compressor assembly and cylinder 6 part of the compressed air compensating assembly: an air storage tank l containing air under constant pressure said tank communicating permanently with cylinder 6 and being provided with-a take- 35 oi l I; an air inlet valve 8 operating to admit air from the atmosphere into cylinder 5 during part of the return stroke of piston 2; and a discharge valve -I0 functioning to permit air under pressure in cylinder 5 to flow into reservoir 1.

The operation of the above described assembly will be better understood by referring to Figs.

I 3 -and'4. In Figure 3, a--b represents the curve the compression stroke and during the return strokean d d-e the aspiration of air from the atmosphere into cylinder 5 via valve 8. Area c--d-e represents the energy furnished during the return stroke by the air confined in the clearance space of cylinder 5. This energy, which varies with the length of compression stroke b-c, is reduced to zero when the clearance space becomes vanishingly small and becomes equal to the energy of compression when the discharge stroke b-c is zero in length. The variation of this energy is represented by the straight line o-p in Figure 4.

Inspection of the left hand portion of Fig. 3 will show that the diagram of'energy furnished by compensating cylinder E and the air under constant pressure in reservoir 1 may be represented by hatched rectangle k-I-m--n, the energy furnished by the air under constant pressure increasing in proportion to the length of the compression stroke. The variations in energy of the air cushion in cylinder 6 are represented in Fig. 4 by straight line r-s sloping in the opposite direction to line o-p. If the sections of pistons `2 and 3 and the volume of the clearance space of the cylinder 5 are properly chosen, the slopes of lines o-p and r-s may be made equal and opposite, that is to say, their sum will be represented by a straight horizontal line passing through point r (in other words, cylinder 8 will act to rigorously compensate deficiencies in return energy derived from the compressed air in cylinder 5) and the total return energyis always sufficient to bring back pistons I to the same point irrespective of variations in the length of the compression stroke of said pistons.

In the variant illustrated in Fig. 2 hollow pistons 5I, integral with pistons 52, slide in motor cylinder 53. Air is compressed in cylinders 5l supporting piston 52 and flows via a valve 63 into a passageiii lying between (l) a rst tube 55 slidably contacting with the interior wall or cylinders inside hollow pistonv 5I and (2) a second tube 59 communicating at opposite extrernities with reservoir 51 containing air under constantpressure and the cylinder 55 inside piston 5I, whence the air discharges through tube 59 into reservoir 51 and through take-olf 6I tothe place of use. 'Ihe air is aspirated from the atmosphere into cylinder 5I via valve 64. It will be seen that cylinder 55 inside piston 5I is the equivaient of cylinder 5 in Fig. 1 and that the two assemblies will operate substantially identically. In

this form of motor-compressor, the air driven outA of compression chamber 54 and circulating through passage 60 serves to cool the piston assembly.

Reservoirs 1 and 51 in Figs. 1 and 2 may be provided with cooling systems oi' any desired type and cooled air for combustion may be led therefrom to motor cylinders 9.

Referring to Fig. 5 of the drawings, there is shown an assembly similar in all respects to the one represented in Fig. 1, except that cylinder l is provided with inlet and exhaust valves Il and Ill operative respectively to draw air from reservoir -1 and to deliver air via. a. conduit I2 to a high pressure air storage reservoir I5.

It will be readily understood that this form of apparatus differs from those illustrated in Figs. 1 and 2 only in being of the two-stage instead of the single stage type.

The cycle of ,this two stage motor-compressor is shown in Fig. 6, wherein the first stage of compression is represented by area. A--B-C-D and the second stage-by area F-G-H-I. These diagrams show the forces actingvon the piston as a function of the latters position. 'I'he aspirating phase occurs during D-A and I-F, the compression phases during A-B and F-G, the reutrnstroke -between B--C and F-G, while expansion ,occurs between C-D and H-I.

If the dimensions of cylinders 5 `and 5 are properly chosen, the compression portions of the diagrams during each of the two stages may be made superposable. The energy for the return stroke of pistons I, 2, 3 is the sum of expansion phases C--D-E and H-I-J-M plus the energy derived from the pressure exerted on piston 3 by the air in the low pressure reservoir 1, this latter energy being represented by rectangle I-F- N-J, since the air is at constant pressure. Inasmuch as the energy derived from areas C-D-E and H-I-L varies linearly with. the length of the compression stroke, their sum will be represented by a straight line O-P (Fig. '7). As already indicated in connection with the descriptions of Figs. 1, 3 and 4, the work effected by the compressed air in cylinder 6 will take the v'and the pressures existing therein to be properly chosen the slopes of lines O-P and R-S may be made exactly equal and opposite and their sum will yield a straight horizontal line R-V corresponding to an 'energy sufiicient to insure the return stroke of the pistons. In other words, as in the case of Fig. 1, the return stroke of the piston will be exactly compensated whatever be the length of the compression stroke.

In theory, exact compensation should be obtained only when the pressures in reservoirs 1 and I5 have a predetermined value. But in practice, it is found that when the dimensions of the various operating elements are properly chosen, the pressures in cylinder 5 may be given a certain range of values.

As will be obvious to those skilled in the art,

the invention is not to be taken as limited to a' combination of only two stages. Obviously the number of stages may be multiplied in accordance with the pressure of air desired.

When two-stage motor-compressors are used,-

it is sometimes necessary to considerably increase the clearance space in the compressor portions in order to obtain sufficient energy for a proper return stroke. This increases the size of the machine to a degree which may become undesirable. Inordertoreduce thesizeofthemachina-an assemblysuchasthatshowninFig-8maybe employed. Here, piston I3 is provided with a hollow cylindrical portion Il receiving a fixed tube I1 air from high pressure air storage reser-v voir 41 passes through an opening Il into tube I1 and cylinder I6 so as to-inprease the energy available for a return strokelr-By increasing the diameter of hollow cylinder II, the energy for the return may be increased as desired.

Fig. 9 shows a similar assembly for increasing Athe energy ofthe return stroke withoutincreasing the volume of the clearance spaces. This assembly diiiers from the one shown in Fig. 8 only in that a second fixed tube Il is inserted inside fixed tube I1 (see also Fig. 2), the air traversing valve Ill moving nrst through a pas-- sage !I into cylinder I5 before passing out through passage Ill into reservoir I5, thus coolin'g the inside of piston 1.

From the foregoing, it will be seen that substantially rigorous compensation is obtained in motor-compressor of the type described, utilizing either single or multiple stages of compression. At the same time, a supply of cooling air is provided for the motor pistons and cylinders.

vIn the claims, the term. rigidly connected applied to the pistons should be interpreted to include the case where the latter are integral with one another. The pistons and cylinders forming part of the motorcompressing and compensating assembliesI will be distinguished by applying the same terms thereto.

What I claim isz- 1. In combination in an internal combustion motor-compressor unit, motor and compressor pistons, motor and-compressing cylinders co-acting with said pistons, said compressing cylinder insaid clearance space.

2. A structure as defined in claim 1 in combination with valve means operative to conduct air from said compressing cylinder to said source of.

3. A structure as dened in claim 1 in combination with means for conducting air from said compressing cylinder to said source of uid under constant pressure and means for cooling the air in said source.

.4. In combination in an internal combustion motor-compressor unit, a motor piston, a motor cylinder supporting said motor piston, a compressing cylinder mounted in line with said motor cylind r and including a clearance space adapted to con ain residual air, and a compressor piston integral with said motorpiston and slidably mounted in said compressing cylinder,-a compensating assembly including a source of fluid under constant pressure reacting on said motor piston and said compressor piston in the direction of their return stroke.

5. In combination in an .internal combustion motor-compressor unit, a motor piston, a motor cylinder supporting said piston, a compressing cylinder mounted in line with said motor cylinder and. including a clearance space adapted to contain residual air, and a compressor piston integral with said motor piston and slidably mounted in said compressing cylinder,a compensating assembly including a compensating piston rigidly attached to said motor and compressor pistons, a cylinder mounted to slidably receive said compensating piston and means for introducing a fluid under constant pressure into said last-named cylinder.

6. In combination in an internal combustion motor-compressor unit, a motor piston, a motor cylinder supporting said piston, a compressing cylinder mounted in line with said motor cylinder and including a clearance space adapted to contain residual air, and a compressor piston rigidly connected to said motor piston and slidably mounted in said compressing cylinder,-a c ompensating assembly including a compensating piston rigidly attached to said motor and compressor pistons, a cylinder mounted to slidably receive said compensating piston, and a reservoir mounted to receive compressed air from said compressor 8. In combination in an internal combustion motor compressor unit, a motor piston, a motor cylinder supporting said piston, a compressing cylinder mounted in line with said motor cylinder and including a clearance space adapted to contain residual air,-a compressor piston rigidly connected to said motor piston and having a hollow portion formed therein, said compressor piston being slidably mounted in said air compressing cylinder, a xed tube mounted inside the hollow portion of said compressor piston, and means for supplying air under constant pressure to said xed tube.

9. In combination'in an internal combustion motor-compressor unit, a motor piston, a motor cylinder s upporting said piston, and a compressing cylinder mounted in line with said motor cylinder and including a clearance space adapted to contain residual air,-a compressor piston rigidly connected to said motor pistonv and having a hollow portion formed therein, said compressor piston being slidably mounted in'said compressing cylinder, a xed tube mounted inside the hollow portions of said compressor piston, and a reservoir adapted to contain a fluid under constant pressur' and communicating with the interior of said hollow tube.

communication between said reservoir and saidthird cylinder.

11. In combination in an internal combustion motor-compressor unit, motor and compressor pis- -tons, motor and compressing cylinders co-acting with said pistons, said compressing cylinder inluding a clearance space adapted to contain residual air under pressure acting as a cushion to vreturn said pistons,-a compensating assembly including a source of iiuid under constant pressure and means for conducting said uid under constant pressure to a point where it reacts on said pistons to supplement the action of the air cushion insaid clearance space, the dimensions of sai'd motor and air compressing cylinders and the pressure from said source being chosen so that said source of iluid under constant pressure acts to supplement the expansion of the air in said clearance spaces during a return stroke to bring said motor piston back to the same point irrespective of the length of the compression stroke.

12. In' combination in an internal combustion motor-compressor unit, freely movable motor and compressor pistons, motor and compressing cylinders coacting with said pistons, said compressing cylinder including a clearance space adapted to contain residual air under pressure. acting as a cushion to return said pistons, said unit including a space of variable volume separate from said compressing cylinder, and means for. supplying to said space a fluid under a pressure which is dependent on the compression pressure of the compressing cylinder whereby said iluid reacts on said pistons to supplement the to supplement the expansion of air in said-'clearance'space during a return stroke to bring said motor piston back to the same point irrespective of the length of the compression stroke.

13. In a device as claimed in claim 12, a tube for conducting away the air compressed by .said unit, said space communicating with said tube.

14. In combination in an internal combustion motor-compressor unit, a motor piston and a plurality of compressor pistons, a motor cylinder and a plurality of compressing cylinders coacting with said pistons, said compressing cylinders including clearance spaces adapted to contain bodies of residual air under pressure acting as cushions to return said pistons, a reservoir connected between said compressing cylinders, a second reservoir connected to said compressing cylinders, said unit including a space separate from said compressing cylinders and connected to said second reservoir whereby the air contained in said second reservoir reacts on said pistons to supplement the action of the air cushions in said clearance spaces and the air in said rst reservoir, the dimensions of said motor and compressing cylinders and the size of said space being so chosen that air from said second reservoir acts to supplement the expansion of the air in said clearance spaces during a return stroke to bring said motor back to the same point irrespective of the length of the compression stroke.

15. In combination in `an internal combustion motor-compressor unit, a motor piston, a low pressure compressor piston and a high pressure compressor piston, a motor cylinder, a low pressure compressing cylinder and a high pressure compressing cylinder coacting with said pistons, said compressing cylinders including clearance spaces adapted to contain bodies of residual air under pressure acting as cushions to return said pistons, a reservoir connected between said compressing cylinders, a second reservoir connected to said high pressure cylinder, said unit including a space separate from said compressing cylinders and connected to said second reservoir whereby the air contained in said second reservoir reacts on said pistons t supplement the action of the air cushions in said clearance spaces and the air in said lrst reservoir.

16. In combination in an internal combustion motor-compressor unit, motor and compressor pistons, motor and compressing cylinders coacting with said' pistons, said motor and compressor pistons having a space therein open at the end remote from the motor cylinder, a reservoir, a tube connected to said reservoir and extending through said open end into said space to a point adjacent the inner end thereof, and means to connect said compressing cylinder to said space, the pressure in said space acting to return the pistons, said tube causing the air to flow through the space so as to cool the pistons. RAUL PATERAS PESCARA. 

